MIDI Controllers
MIDI controllers are channel-specific, with the exception of poly pressure messages. They affect the entire voice, regardless of whether they are inserted for a part or a note.
The fact that MIDI controllers are channel-specific limits the potential of note expression to monophonic (solo) performances. If you edit articulation data on one note, this affects all other notes of the same voice, that is, any other note playing on the same channel at the same time.
The MPE standard, however, allows you to assign each note to a different MIDI channel, and thereby to control notes individually. The standard recommends to use exclusively the MIDI channel messages pitchbend, aftertouch, and CC 74 to control individual notes. In this scenario, MIDI channel 1 controls all notes, whereas the other 15 MIDI channels can control individual notes.
To control individual notes via MIDI controllers, set the MIDI channel of the track to Any.